1. Field of the Invention
The present invention relates to laser-scanning fluoroscopy apparatuses.
2. Description of Related Art
In a fluoroscopy apparatus for emitting excitation light onto a tissue to examine fluorescence generated by the tissue, it is necessary to separate fluorescence from excitation light to detect the fluorescence. A dichroic mirror is normally used in known methods for separating fluorescence from excitation light. However, since the wavelength of excitation light entering the tissue is close to that of fluorescence generated by that excitation light, it is often difficult to design a dichroic mirror that can efficiently separate fluorescence from excitation light.
In order to overcome this difficulty, a method for separating fluorescence from excitation light using a spectroscopic device, such as a prism, is proposed (see, for example, U.S. Pat. No. 5,751,417, PCT Japanese Translation Patent Publication No. Hei-9-502269, and Japanese Unexamined Patent Application Publication No. 2001-272275).
U.S. Pat. No. 5,751,417 discloses a confocal fluorescence microscope apparatus that does not use a dichroic mirror. This confocal fluorescence microscope apparatus includes an aperture for converting light emitted from a light source into a plurality of light strips; a prism; and a mirror for selectively reflecting part of each light strip split by the prism to separate fluorescence returning from a tissue and excitation light by causing the fluorescence to pass through a slit provided at the mirror, thus allowing a photodetector to detect the separated fluorescence.
PCT Japanese Translation Patent Publication No. Hei-9-502269 discloses an apparatus for selectively detecting light with at least two spectral bands in a beam using a prism and a mirror having an aperture. Japanese Unexamined Patent Application Publication No. 2001-272275 discloses an apparatus for selectively detecting at least one spectral region of a beam in the beam path of a confocal scanning microscope using a prism and a triangular mirror.
Although the confocal fluorescence microscope described in U.S. Pat. No. 5,751,417 can separate fluorescence from excitation light without a dichroic mirror, it cannot detect a plurality of fluorescence beams generated by simultaneously emitting a plurality of excitation light beams. In other words, although the confocal fluorescence microscope described in U.S. Pat. No. 5,751,417 can change the wavelength of excitation light and the wavelength of fluorescence to be passed through the slit by mirror reflection by moving the mirror in a direction intersecting with the optical axis, it is difficult to simultaneously emit excitation light with a plurality of wavelengths and to simultaneously detect fluorescence with a plurality of wavelengths.
Furthermore, although the apparatuses described in PCT Japanese Translation Patent Publication No. Hei-9-502269 and Japanese Unexamined Patent Application Publication No. 2001-272275 can selectively detect light with a plurality of wavelengths, these apparatuses require a plurality of apertures and a plurality of triangular mirrors to be arranged at certain intervals. This is disadvantageous in that the structures become complicated and the sizes of the apparatuses increase. In addition, a plurality of apertures and triangular mirrors need to be adjusted individually, making it difficult to detect light with high accuracy due to this adjustment procedure.